Power switches are used e.g. in DC-DC power converters to toggle the power converters between different modes or states. Applications for such power converters are e.g. LED based light bulbs or portable application (for charging the battery of a portable electronic device). In this context a power switch, e.g. a transistor such as a metal oxide semiconductor (MOS) field effect transistor (FET), is switched between an on-state and an off-state at a pre-determined commutation cycle rate. The commutation cycle rate is typically in the range of 10 KHz to several MHz, but it is desirable to further increase the commutation cycle rate in order to allow for a further integration of the DC-DC power converters. In particular, when increasing the commutation cycle rate or the clock rate, the size of external components of the DC-DC power converters, such as coils, transformers and/or capacitors may be reduced, thereby allowing for a reduction of the size of the DC-DC power converter. By way of example, for power converters in portable applications (comprising e.g. rechargeable battery systems) the clock rate may be in the range of 1 MHz or higher.
In order to put a power switch, e.g. a MOSFET, into the on-state, a gate voltage may be applied to a gate of the power switch, thereby charging a gate capacitance of the power switch. On the other hand, in order to put the power switch into the off-state, the gate of the power switch may be coupled to ground, thereby discharging the gate capacitance of the power switch. As such, the gate capacitance of the power switch is charged and discharged at the commutation cycle rate. The gate charge (i.e. the charge of the gate capacitance) adds to the losses of the power converter comprising the power switch. These losses increase with increasing commutation cycle rate. Hence, the losses due to the gate charge are expected to become a serious issue, when operating DC-DC power converters with increased commutation cycle rates.
The present document addresses the above mentioned technical problem. In particular, the present document describes a circuit arrangement and a method for commutating a power switch with reduced losses.